The invention relates to a new class of viruses having the capacity to cause lymphadenopathies, which are then capable of being replaced by acquired immune deficiency syndrome (AIDS) in man. The invention also relates to antigens capable of being recognized by antibodies induced in man by this new class of virus. It also relates to the antibodies induced by antigens obtained from these viruses.
This invention relates, furthermore, to cloned DNA sequences possessing sequence analogy or complementarity with the genomic RNA of the above-mentioned virus. It also relates to the methods for preparing these cloned DNA sequences.
The invention also relates to polypeptides containing amino acid sequences encoded by the cloned DNA sequences.
In addition, the invention relates to applications of these antigens to the in vitro diagnosis in man of potentials for certain forms of AIDS and, in respect of some of these antigens, to the production of immunogenic compositions and vaccinating compositions against this retrovirus The invention likewised relates to the applications of the above-mentioned antibodies for the same purposes.
Finally, the invention relates to the application of the cloned DNA sequences, and of polypeptides obtained from these sequences, as probes in diagnostic kits.
The isolation and characterization of a first retrovirus, known as LAV, whose responsibility in the development of AIDS had been recognized, formed the subject of a description in a paper by F. BARRE-SINOUSSI et al. already in 1983 (Science, vol. 220, No. 45-99, 20, p. 868-871). Application of some extracts of this virus, and more especially of some of its proteins, to the diagnosis of the presence of antibodies against the virus was described more especially in European Patent Application No. 138.667. Since then, other similar strains and some variants of LAV have been isolated. Examples which may be recalled are those known by the names HTLV-III and ARV.
To apply the new rules of nomenclature published in Nature in May 1986, the retroviruses capable of inducing in man the above-mentioned lymphadenopathies and AIDS will be given the overall designation xe2x80x9cHIVxe2x80x9d, an abbreviation of the term xe2x80x9cHuman Immunodeficiency Virusxe2x80x9d. The subgroup of retroviruses formed by LAV and its variants was initially designated by the terms xe2x80x9cLAV type Ixe2x80x9d or xe2x80x9cLAV-Ixe2x80x9d. The latter subgroup will be designated hereinafter HIV-1, it being understood that the term LAV will still be retained to denote that strain, among the strains of retrovirus (in particular LAAV, IDAV-4 and IDAV-2) belonging to. the HIV-1 virus class which are described in the above-mentioned European Patent Application 138,667, which was used in the comparative experiments described later, namely LAVBRUxe2x80x2 which was deposited with the Collection National des Cultures de Micro-organismes (CNCM) (National Collection of Micro-organism Cultures) of the Institute Pasteur de Paris, France, on Jul. 15, 1983 under No. I-232.
The new retrovirus which forms the subject of the present patent and the virus strains which are related to it and which are, like it, capable of multiplying in human lymphocytes, formerly known as. xe2x80x9cLAV type IIxe2x80x9d or xe2x80x9cLAV-IIxe2x80x9d, are henceforward known as xe2x80x9cHIV-2xe2x80x9d, it being understood that the designations of certain HIV-2 isolates described later will be followed by three letters which refer to the patients from whom they were isolated.
The xe2x80x9cHIV-2xe2x80x9d group can be defined as a group of viruses having in vitro a tropism for human T4 lymphocytes, and which have a cytopathogenic effect with respect to these lymphocytes when they multiply therein, and then either cause generalized and persistent polyadenopathies or one of the forms of AIDS. The HIV-2 retroviruses have proved to be different from the HIV-1 type viruses under the conditions mentioned later. Like these latter viruses, they are different from the other human retroviruses which are already known (HTLV-I and HTLV-II).
Although there is fairly wide genetic variability in the virus, the different HIV-1 strains isolated to date from American, European, Haitian and African patients have antigenic sites in common conserved on their principal proteins, i.e. core protein p25, envelope glycoprotein gp110 and transmembrane protein gp41-43. This relationship makes it possible, for example, for the prototype LAV strain to be used as a strain of antigens for detecting antibodies against all HIV-1 class viruses, in all people who carry them, regardless of their origin. This strain is hence currently used for detecting anti-HIV-1 antibodies in blood donors and patients, in particular by immunofluorescence and in particular by the technique known as ELISA, xe2x80x9cWestern Blotxe2x80x9d (or immuno-imprinting) and xe2x80x9cRIPAxe2x80x9d, an abbreviation for Radioimmunoprecipitation Assay.
However, in a serological study performed with an HIV-1 lysate on patients who originated from West Africa, it was observed that some of them gave seronegative or very weakly positive reactions, whereas they showed clinical and immunological signs of AIDS.
The cultured lymphocytes of one of these patients were the source of a first HIV-2 retrovirus isolated, whose structure in electron microscopy and whose protein profile in SDS gel electrophoresis show a resemblance to those of HIV-1. However, this new retrovirus HIV-2 possesses overall only a slight relationship to HIV-1, from the standpoint both of the antigenic homology of its proteins and of the homology of its genetic material.
This new retrovirus, or retroviruses having equivalent antigenic and immunological properties, can hence constitute sources of antigens for the diagnosis of infection by this virus and the variants which induce an AIDS farm of the type which had been observed in the initial instances in African patients or in people who had spent time in Africa.
Typically, this virus was isolated from the blood, drawn in the presence of heparin, from a 28-year-old heterosexual patient who had never been transfused and who was not a drug addict. Since 1983, he had had substantial chronic diarrhea, and substantial weight loss (17 kg) with intermittent fever. More recently, he had had Candida and Serratia infections, including an oesophageal candidiasis typical of AIDS.
This patient also had anemia, cutaneous anergy, lymphopenia and a T4 lymphocyte/T8 lymphocyte ratio of 0.15, with a T4 lymphocyte level of less than 100 per mm3 of serum. His lymphocytes in culture did not respond to stimulation with phytohaemagglutinin and concanaval in A. This patient was also diagnosed as suffering from recurrent bacteremia due to S. enteriditis, cryptosporidioses, infections due to Isospora belli and cerebral toxoplasmosis.
This combination of signs was evidence of xe2x80x9ccomplex symptoms linked with AIDSxe2x80x9d or xe2x80x9cARCxe2x80x9d (abbreviation for xe2x80x9cAIDS-Related Complexxe2x80x9d), of the type caused by HIV-1 virus. These various observations were also in conformity with the criteria applied by the Center of Disease Control (CDC) of Atlanta, USA.
The culturing of the lymphocytes from these patients and the isolation of the retrovirus were performed according to the technique already described for the isolation of HIV-1 in the paper by BARRE-SINOUSSI et al. and European Patent Applicatfion No. 84/401.834-0.138.667. They are recalled briefly below. Lymphocytes stimulated for 3 days with phytohaemagglutinin (PHA) were cultured in RPMI 1640 culture medium to which 10% of foetal calf serum and 10xe2x88x925 M xcex2-mecaptoethanol, interleukin-2 and anti-(human interferon xcex1) serum are added.
The production of virus was followed by its reverse transcriptase activity. In the culture supernatant, the peak viral activity appeared at between day 14 and day 22, and then decreased. The decline and death of the cell culture followed. As with HIV-1, sections of lymphocytes infected with HIV-2 showed, in electron microscopy, virions which had reached maturity, and viral particles budding at the surface of the infected cells. The cell lines used for producing the cultures of these isolated viruses can be, depending on the case, cell lines of the HUT, CEM or MOLT type, or any immortalized lymphocyte line bearing T4 receptors.
The virus was then propagated in cultures of lymphocytes from blood donors, and then in continuous lines of leukaemic origin, such as HUT 78. It was then characterized by its antigens and its nucleic acid as being substantially different from HIV-1. The virus was purified as described in the prior documents already mentioned. A first isolate of this virus was deposited with the CNCM on Dec. 19, 1985 under No. I-502. It was subsequently designated by the name LAV-II MIR. A second isolate was deposited with the CNCM on Feb. 21, 1986 under No. I-532. This second isolate has the reference name LAV-II ROD. These isolates will sometimes be referred to later simply as MIR or ROD.
In a general manner, the invention relates to any variant of the above viruses, or any equivalent virus (for example, such as HIV-2-IRMO and HIV-2-EHO, deposited with the CNCM on Dec. 19, 1986 under Nos. I-642 and I-643, respectively), containing structural proteins which have the same immunological propeties as those of the HIV-2 viruses deposited with the CNCM under Nos. I-502 or I-532. The definitions of criteria of equivalence will be returned to later.
The invention also relates to a method for producing the HIV-2 virus or variants of the latter in permanent cell lines derived from T4 lymphocytes, or lymphocytes bearing the T4 phenotype, this method consisting in culturing these lines which have been infected beforehand with HIV-2 virus and, in particular when the Level of reverse transcriptase activity has reached a specified threshold, in recovering the amounts of virus released into the culture medium.
A preferred permanent line for the purpose of culturing HIV-2 is, for example, of the HUT 78 cell type. An HUT 78 line infected with HIV-2 was deposited on Feb. 6, 1986 with the CNCM under No. I-519. Culturing is, for example, carried out as follows:
The HUT 78 cells (106/ml) are co-cultured with infected normal human lymphocyte (106/ml). The culture medium is RPMI 1640 with 10% foetal calf serum. After 15 to 21 days, a cytopathogenic effect is observed in the HUT 78 cells. The reverse transcriptase is assayed one week after this observation, in the culture supernatant. It is then possible to begin to recover the virus from this supernatant.
Another preferred line for culturing belongs to the lines known under the designation CEM.
The infection and then the culturing of the infected CEM cells can be carried out, in particular, as follows.
T4 lymphocytes infected beforehand with HIV-2 virus and uninfected cells of the CEM line are co-cultured for the time required for infection of the CEM. The culture conditions are then, moreover, continued in a suitable medium, for example that described below, and when the reverse transcriptase activity of the infected cells has reached a sufficient level, the virus produced is recovered from the culture medium.
In particular, co-culturing was carried out, under the conditions specified below, of human T4 lymphocytes which had been infected five days beforehand with a strain of HIV-2 virus originating from a patient hereinafter designated xe2x80x9cRODxe2x80x9d, on the one hand, and CEM, on the other hand.
The infected T4 lymphocytes, activated before-hand with phytohaemagglutinin, proved to possess a reverse transcriptase activity of 5.000 cpm/106 normal T lymphocytes three days after the beginning of the infection. Culturing was continued until the measured reverse transcriptase activity reached 100.000 cpm in the supernatant. These T4 lymphocytes were then placed in contact with CEM cells (3xc3x97106 infected normal T lymphocytes) and reincubated in the following culture medium: RPMI 1640 containing 2.92 mg/ml of L-glutamine, 10% of decomplemented foetal calf serum, 2 mg/ml of Polybrene, 0.05% of anti-interferon-alpha serum, 100.000 mg/ml of penicillin, 10 mg/ml of streptomycin and 10.000 mg/ml of neomycin.
The culture medium is changed twice weekly.
The measurements of reverse transcriptase activity measured in the supernatant were as follows:
A CEM culture infected with HIV-2 virus was deposited with the Collection Nationale de Cultures de Micro-organismes (CNCM) of the Institut Pasteur under no. I-537 on Mar. 24, 1986.
A few characteristics of the antigens and nucleic acids involved in the structure of HIV-2 emerge from the experiments carried out under the conditions described below. They will, in many cases, be better assessed by comparison with the same type of characteristics relating to other types of retrovirus, in particular HIV-1 and SIV.